1. Field of the Invention
This invention relates generally to devices which are used to sharpen a cutting surface. More specifically, the invention relates to a device for sharpening cutting edges on chain saw cutter teeth which have a concave surface next to at least one of their cutting edges.
2. Description of the Prior Art
Chain saws, of course, have long been common use for cutting timber and other material, both in the United States and throughout the world. As with any cutting instrument, the cutting edges on the individual cutter links which make up a saw chain grow dull after time. Rather than discard a dull chain and replace it with a new one, it is generally more economical to re-sharpen the chain. However, due to the irregular shape of the cutting edges on many of the different types of chain saw teeth and the difficulty of holding the tooth during sharpening, resharpening in the past has often been time consuming and frustrating.
Various machines have been proposed for sharpening the cutter link edges on a saw chain. An example of such a machine is disclosed in U.S. Pat. No. 4,732,056 to Foster. In this device, a saw chain is guided by a pair of guide wheels past a rotatable abrasive wheel, which engages and sharpens the cutting edges. The abrasive wheel in Foster is beveled so as to provide a better engagement angle with the cutting edges of the various lengths.
One disadvantage of sharpening machines such as that disclosed in the Foster patent is that they are relatively complicated and expensive, which effectively precludes their use by all persons or entities who do not have a large volume of dull chains to sharpen. Moreover, certain types of chain saws have one or more curved cutting edges which cannot be sharpened by advancing the individual links linearly with respect to an abrasive surface, which is the process used in many prior art sharpening machines. A further disadvantage of many of the prior art sharpening machines is that they require removal of the chain from the saw prior to sharpening.
It is clear that there has existed a long and unfilled need in the prior art for a chain saw sharpening device which is simple and inexpensive, which is efficient at sharpening cutter links having one or more curved cutting edges and which is capable, if desired, of sharpening a chain saw link cutting edge while the chain is still positioned on a saw.